CMOS transistors including gate spacers of the same thickness

ABSTRACT

A dielectric material layer is deposited on gate structures of first and second semiconductor material portions. The dielectric material layer is anisotropically etched to form a first gate spacer on a first semiconductor material portion, while being protected above the second semiconductor material portion. After formation of first raised active regions on the first semiconductor material portion, a dielectric stack of a dielectric oxide liner and a dielectric nitride liner is formed. The dielectric stack is removed over the second semiconductor material portion and a second gate spacer is formed on the second semiconductor material portion, while the dielectric stack protects the first raised active regions. A second gate spacer is formed by anisotropically etching the dielectric material layer over the second semiconductor material portion. The first and second gate spacers have the same composition and thickness. Second raised active regions can be formed on the second semiconductor material portion.

BACKGROUND

The present disclosure relates to semiconductor structures, andparticularly to complementary metal oxide semiconductor (CMOS) fieldeffect transistors (FETs) including gate spacers of the same thicknessand a method of manufacturing the same.

A CMOS circuit includes p-type transistors and n-type transistors. If aprocess integration scheme employing two separate epitaxial depositionprocesses are employed to form the raised active regions of the p-typetransistors and the raised active regions of the n-type transistors, onetype of transistors needs to be covered with a dielectric layer while aselective epitaxy process is performed on physically exposedsemiconductor surfaces of the other type of transistors. The inherentasymmetry in the dielectric material stack during formation of gatespacers for the two types of transistors results in thicker gate spacersfor the type of transistors on which a second selective epitaxy processis performed. The difference in the thicknesses of the gate spacersacross the two types of transistors results in a difference in theextension length across the two types of transistors when epitaxialfilms are used for doping source and drain extension regions, which canadversely impact the device performance. In view of the deleteriouseffect due to the differences in the thicknesses of the gate spacers ofdifferent types of transistors, a scheme for providing the samethickness for the gate spacers of all types of transistors on a samesubstrate is desired.

SUMMARY

A dielectric material layer is deposited on gate structures of first andsecond semiconductor material portions to be employed for active regionsof a p-type transistor and an n-type transistor. The dielectric materiallayer is anisotropically etched to form a first gate spacer on a firstsemiconductor material portion (which can be for p-type transistor orfor an n-type transistor), while the dielectric material layer isprotected above a second semiconductor material portion. After formationof first raised active regions on the first semiconductor materialportion, a dielectric stack of a dielectric oxide liner and a dielectricnitride liner is formed on the first semiconductor material portion andthe remaining portion of the dielectric material layer. The dielectricstack is removed over the second semiconductor material portion and asecond gate spacer is formed on the second semiconductor materialportion, while the dielectric stack protects the first raised activeregions. A second gate spacer is formed by anisotropically etching thedielectric material layer over the second semiconductor materialportion. The first and second gate spacers have the same composition andthe same thickness. Second raised active regions can be formed on thesecond semiconductor material portion.

According to an aspect of the present disclosure, a method of forming asemiconductor structure is provided. A first gate structure straddling afirst semiconductor material portion in a first device region and asecond gate structure straddling a second semiconductor material portionin a second device region are formed on a substrate. A dielectricmaterial layer is formed on the first and second gate structures. Afirst gate spacer is formed by anisotropically etching a first portionof the dielectric material layer in the first device region while asecond portion of the dielectric material layer is masked in the seconddevice region. A dielectric stack including dielectric material linersis formed over the first semiconductor material portion and the secondportion of the dielectric material layer. A portion of the dielectricstack is removed from the second device region. A second gate spacer isformed by anisotropically etching the second portion of the dielectricmaterial layer while the dielectric stack masks the first semiconductormaterial portion.

According to another aspect of the present disclosure, a semiconductorstructure includes a first gate structure straddling a firstsemiconductor material portion on a substrate, a second gate structurestraddling a second semiconductor material portion on the substrate,first raised active regions located on the first semiconductor materialportion, second raised active regions located on the secondsemiconductor material portion, a dielectric stack contacting the firstraised active regions and the first gate structure, and not in physicalcontact with the second raised active regions, and a material layerincluding a dielectric material and in physical contact with thedielectric stack and surfaces of the second raised active regions.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a top-down view of an exemplary semiconductor structure afterformation of semiconductor fins by patterning a top semiconductor layerof a semiconductor-on-insulator (SOI) substrate according to anembodiment of the present disclosure.

FIG. 1B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 1A according to an embodiment of thepresent disclosure.

FIG. 2A is a top-down view of the exemplary semiconductor structureafter formation of disposable gate structures according to an embodimentof the present disclosure.

FIG. 2B is a vertical cross-sectional view of the exemplarysemiconductor structure FIG. 2A according to an embodiment of thepresent disclosure.

FIG. 3A is a top-down view of the exemplary semiconductor structureafter formation of a dielectric material layer and a first patternedmask layer according to an embodiment of the present disclosure.

FIG. 3B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 3A according to an embodiment of thepresent disclosure.

FIG. 4A is a top-down view of the exemplary semiconductor structureafter formation of a first gate spacer and removal of the firstpatterned mask layer according to an embodiment of the presentdisclosure.

FIG. 4B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 4A according to an embodiment of thepresent disclosure.

FIG. 5A is a top-down view of the exemplary semiconductor structureafter formation of first raised active regions by a first selectiveepitaxy process according to an embodiment of the present disclosure.

FIG. 5B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 5A according to an embodiment of thepresent disclosure.

FIG. 6A is a top-down view of the exemplary semiconductor structureafter formation of a dielectric stack of a dielectric oxide liner and adielectric nitride liner according to an embodiment of the presentdisclosure.

FIG. 6B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 6A according to an embodiment of thepresent disclosure.

FIG. 7A is a top-down view of the exemplary semiconductor structureafter formation of a second patterned mask layer and removal ofphysically exposed portions of the dielectric nitride liner according toan embodiment of the present disclosure.

FIG. 7B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 7A according to an embodiment of thepresent disclosure.

FIG. 8A is a top-down view of the exemplary semiconductor structureafter removal of physically exposed portions of the dielectric oxideliner according to an embodiment of the present disclosure.

FIG. 8B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 8A according to an embodiment of thepresent disclosure.

FIG. 9A is a top-down view of the exemplary semiconductor structureafter formation of a second gate spacer by an anisotropic etch of aphysically exposed portion of the dielectric material layer according toan embodiment of the present disclosure.

FIG. 9B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 9A according to an embodiment of thepresent disclosure.

FIG. 10A is a top-down view of the exemplary semiconductor structureafter formation of second raised active regions by a second selectiveepitaxy process according to an embodiment of the present disclosure.

FIG. 10B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 10A according to an embodiment of thepresent disclosure.

FIG. 11A is a top-down view of the exemplary semiconductor structureafter formation of a diffusion barrier liner and a planarizationdielectric layer according to an embodiment of the present disclosure.

FIG. 11B is a vertical cross-sectional view of the exemplarsemiconductor structure of FIG. 11A according to an embodiment of thepresent disclosure.

FIG. 12A is a top-down view of the exemplary semiconductor structureafter formation of various contact via structures according to anembodiment of the present disclosure.

FIG. 12B is a vertical cross-sectional view of the exemplarysemiconductor structure of FIG. 12A according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure relates to complementary metaloxide semiconductor (CMOS) field effect transistors (FETs) includinggate spacers of the same thickness and a method of manufacturing thesame. Aspects of the present disclosure are now described in detail withaccompanying figures. It is noted that like reference numerals refer tolike elements across different embodiments. The drawings are notnecessarily drawn to scale. As used herein, ordinals such as “first” and“second” are employed merely to distinguish similar elements, anddifferent ordinals may be employed to designate a same element in thespecification and/or claims.

Referring to FIGS. 1A and 1B, an exemplary semiconductor structureaccording to an embodiment of the present disclosure includessemiconductor material portions (30, 40) provided on an insulator layer20. A handle substrate 10 can be provided underneath the insulator layer20 to provide mechanical support to the insulator layer 20 and thesemiconductor material portions (30, 40). The handle substrate 10 can bea semiconductor layer, an insulator layer, or a conductive materiallayer. The insulator layer 20 includes an insulator material such assilicon oxide.

The semiconductor material portions (30, 40) can be formed by providinga semiconductor-on-insulator layer including, from bottom to top, thehandle substrate 10, the insulator layer 20, and a top semiconductorlayer, and subsequently patterning the top semiconductor layer. The topsemiconductor layer can be patterned, for example, by application andlithographic patterning of a photoresist layer and subsequent patterntransfer into the top semiconductor layer employing an anisotropic etch.The photoresist layer can be removed, for example, by ashing.

At least one first semiconductor material portion 30 can be formed in afirst device region 100, and at least one second semiconductor materialportion 40 can be formed in a second device region 200. In oneembodiment, the at least one first semiconductor material portion 30 canbe at least one first semiconductor fin, and the at least one secondsemiconductor material portions 40 can be at least one secondsemiconductor fin. As used herein, a “semiconductor fin” refers to asemiconductor material portion having a parallel pair of verticalsidewalls that extend along a lengthwise direction. As used herein, a“lengthwise direction” of an element refers to a direction that isparallel to an axis of rotation of the element that passes through thecenter of mass and around which the moment of inertia is minimized.

The semiconductor material portions (30, 40) include at least onesemiconductor material, which can be a Group IV semiconductor material,a compound semiconductor material, and/or an organic semiconductormaterial. Further, the at least one semiconductor material can be singlecrystalline, polycrystalline, or amorphous. In one embodiment, thesemiconductor material portions (30, 40) include a single crystallinesemiconductor material. The height of each semiconductor materialportions (30, 40) can be in a range from 30 nm to 200 nm, althoughlesser and greater heights can also be employed. The width of eachsemiconductor material portion (30, 40) can be in a range from 10 nm to100 nm, although lesser and greater widths can also be employed.

The first and second semiconductor material portions (30, 40) can beindependently doped with p-type dopants and/or with n-type dopants. Inone embodiment, the at least one first semiconductor material portion 30can have a doping of a first conductivity type, and the at least onesecond semiconductor material portion 40 can have a doping of a secondconductivity type that is the opposite of the first conductivity type.The first conductivity type can be p-type and the second conductivitytype can be n-type, or vice versa.

Referring to FIGS. 2A and 2B, gate structures (51, 53, 55) can be formedacross each of the semiconductor material portions (30, 40). The gatestructures (51, 53, 55) can include a first gate structure (51, 53, 55)formed in the first device region 100 and a second gate structure (51,53, 55) formed in the second device region 200. Thus, the first gatestructure (51, 53, 55) straddles at least one first semiconductormaterial portion 30 in the first device region 100 on a substrate (10,20), and the second gate structure (51, 53, 55) straddles the at leastone second semiconductor material portion 40 in the second device region200 on the substrate (10, 20).

In one embodiment, the gate structures (51, 53, 55) can be disposablegate structures, i.e., gate structures that can be subsequently removed.In one embodiment, the gate structures (51, 53, 55) can include avertical stack of multiple material portions. For example, each gatestructure (51, 53, 55) can include a vertical stack, from bottom to top,of a disposable material portion 51, a first dielectric cap 53, and asecond dielectric cap 55. In one embodiment, the semiconductor materialportions (30, 40) can include single crystalline silicon, the disposablematerial portions 51 can include germanium or a silicon germanium alloyin which the atomic concentration of germanium is greater than 50%, thefirst dielectric caps 53 can include silicon oxide, and the seconddielectric caps 55 can include silicon nitride. The height of each gatestructure (51, 53, 55), as measured from the topmost surfaces of thesemiconductor material portions (30, 40), can be in a range from 100 nmto 400 nm, although lesser and greater thicknesses can also be employed.

While the present disclosure is described employing an embodiment inwhich the gate structures (51, 53, 55) are disposable structures,embodiments are expressly contemplated in which permanent gatestructures are employed in lieu of disposable gate structures. In thiscase, each permanent gate structure include, from bottom to top, a gatedielectric and a gate electrode in lieu of a vertical stack, from bottomto top, of a disposable material portion 51, a first dielectric cap 53,and a second dielectric cap 55.

Referring to FIGS. 3A and 3B, a dielectric material layer 60 can beformed on physically exposed surfaces of the semiconductor materialportions (30, 40) and the gate structures (51, 53, 55). The dielectricmaterial layer 60 includes a dielectric material such as siliconnitride, silicon oxynitride, a dielectric metal oxide, a dielectricmetal nitride, or a combination thereof. In one embodiment, thedielectric material layer 60 includes a dielectric material differentfrom the dielectric material of the insulator layer 20. For example, theinsulator layer 20 can include silicon oxide, and the dielectricmaterial layer 60 can include a dielectric material different fromsilicon oxide.

The dielectric material layer 60 can be formed by a conformal depositionmethod such as chemical vapor deposition (CVD) or atomic layerdeposition (ALD). In one embodiment, the dielectric material layer 60can be formed by low pressure chemical vapor deposition (LPCVD). Thethickness of the dielectric material layer 60 can be, for example, from3 nm to 30 nm, although lesser and greater thicknesses can also beemployed.

A first patterned mask layer 57 is formed over the second device region200, while the first device region 100 is not covered by the firstpatterned mask layer 57. The first patterned mask layer 57 can be, forexample, a patterned photoresist layer. In this case, a blanketphotoresist layer can be formed in the first and second device regions(100, 200) over the semiconductor material portions (30, 40) and thegate structures (52, 53, 55), and can be lithographically patterned suchthat the remaining portion of the photoresist layer is present only inthe second device region 200 and is not present in the first deviceregion 100.

Referring to FIGS. 4A and 4B, an anisotropic etch is performed to removehorizontal portions of the physically exposed portions of the dielectricmaterial layer 60 within the first device region 100, while the firstpatterned mask layer 57 covers the dielectric material layer 60 in thesecond device region 200. A contiguous remaining vertical portion of thedielectric material layer 60 laterally surrounding, and contacting, thefirst gate structure (51, 53, 55) in the first device region 100constitutes a first gate spacer 62. Thus, the first gate spacer 62 canbe formed by anisotropically etching a first portion of the dielectricmaterial layer 60 in the first device region 100 while a second portionof the dielectric material layer 60 is masked in the second deviceregion 200. The anisotropic etch can be, for example, a reactive ionetch. The first gate spacer 62 includes the same material as thedielectric material layer 60.

Referring to FIGS. 5A and 5B, first active regions (3S, 3D) can beformed by introducing electrical dopants into portions of the at leastone first semiconductor material portions 30 that are not masked by thefirst gate structure (51, 53, 55) and the first gate spacer 62. As usedherein, “active regions” collectively refer to a source region and adrain region of a field effect transistor. Each unimplanted portion ofthe at least one first semiconductor material portion 30 constitutes afirst body region 3B, which contacts a first source region 3S and afirst drain region 3D at p-n junctions. The first patterned mask layer57 can be employed to prevent implantation of the electrical dopantsinto any portion of the at least one second semiconductor materialportion 40.

The first patterned mask layer 57 can be removed selective to thedielectric material layer 60, the at least one first semiconductormaterial portion (3S, 3D, 3B), and the first gate structure (51, 53,55), for example, by ashing. While the present disclosure is describedemploying an embodiment tin which the first active regions (3S, 3D) areformed after formation of the first gate spacer 62, embodiments in whichthe first active regions (3S, 3D) are formed prior to formation of thefirst gate spacer 62 are expressly contemplated herein.

First raised active regions (5S, 5D) can be formed by selectivedeposition of a semiconductor material on the surfaces of the firstactive regions (3S, 3D). During the selective deposition, thesemiconductor material is deposited only on semiconductor surfaces, anddoes not nucleate on dielectric surfaces such as the surfaces of thedielectric material layer 60, the first gate spacer 62, and the firstand second dielectric caps (53, 55). Thus, the first raised activeregions (5S, 5D) can be formed on the at least one first semiconductormaterial portion (3S, 3D, 3B), while the second portion of thedielectric material layer 60 that remains in the second device region200 masks the at least one second semiconductor material portion 40.

The first raised active regions (3S, 3D) can be deposited with in-situdoping of electrical dopants, or can be deposited as an intrinsicsemiconductor material and subsequently doped with electrical dopants,for example, by a masked ion implantation process. The selectivedeposition can be performed, for example, employing a selective epitaxyprocess in which single crystalline semiconductor material portions areformed directly on the surfaces of the first active regions (3S, 3D). Inthis case, the first raised active regions (5S, 5D) can be epitaxiallyaligned to the at least one first semiconductor material portion (3S,3D, 3B).

Referring to FIGS. 6A and 6B, a dielectric stack (66, 68) of adielectric oxide liner 66 and a dielectric nitride liner 68 can beformed directly on physically exposed surfaces of the remaining portionof the dielectric material layer 60, the first raised active regions(5S, 5D), the first gate structure (51, 53, 55), the first gate spacer62, and the insulator layer 20. The dielectric oxide liner 66 includes adielectric oxide material such as silicon oxide. The dielectric nitrideliner 68 includes a dielectric nitride material such as silicon nitrideor a dielectric metal nitride. The dielectric oxide liner 66 and thedielectric nitride liner 68 can be deposited, for example, by chemicalvapor deposition (CVD) or atomic layer deposition (ALD). The thicknessof the dielectric oxide liner 66 can be in a range from 1 nm to 10 nm,although lesser and greater thicknesses can also be employed. Thethickness of the dielectric nitride liner 68 can be in a range from 1 nmto 20 nm, although lesser and greater thicknesses can also be employed.

Referring to FIGS. 7A and 7B, a second patterned mask layer 59 is formedover the first device region 100, while the second device region 200 isnot covered by the second patterned mask layer 59. The second patternedmask layer 59 can be, for example, a patterned photoresist layer. Inthis case, a blanket photoresist layer can be formed in the first andsecond device regions (100, 200) over the semiconductor materialportions (30, 40), the first raised active regions (5S, 5D), the gatestructures (52, 53, 55), and the remaining portions of the dielectricmaterial layer 60, and can be lithographically patterned such that theremaining portion of the photoresist layer is present only in the firstdevice region 100 and is not present in the second device region 200.

Physically exposed portions of the dielectric nitride liner 68 isremoved employing the second patterned mask layer 59 as an etch mask.The dielectric nitride liner 68 can be removed from the second deviceregion 200, for example, by an isotropic etch such as a wet etch or achemical downstream etch (CDE). For example, if the dielectric nitrideliner 68 includes silicon nitride, a wet etch employing a combination ofethylene glycol and hydrofluoric acid can be employed to remove thedielectric nitride liner 68. The duration of the isotropic etch can betimed such that the dielectric oxide liner 66 remains at least partiallyin the second device region 200 after the isotropic etch. Alternatively,an anisotropic etch can be employed in lieu of the isotropic etchprovided that the anisotropic etch can remove the dielectric nitrideliner 68 selective to the dielectric oxide liner 66.

Referring to FIGS. 8A and 8B, the dielectric oxide liner 66 can beremoved selective to the dielectric material layer 60 by another etch,which can be an isotropic etch such as a wet etch or a vapor etch. Forexample, if the dielectric oxide liner 6 includes silicon oxide, a wetetch employing hydrofluoric acid or a vapor etch employing a vapor ofhydrofluoric acid can be employed to remove the dielectric oxide liner66. The etch can be selective to the material of the dielectric materiallayer 60. Thus, the dielectric material layer 60 is not etched duringremoval of the dielectric oxide layer 66 from the second device region200. Thus, the portion of the dielectric stack (66, 68) in the seconddevice region 200 is removed employing the second patterned mask layer59 as an etch mask.

Referring to FIGS. 9A and 9B, an anisotropic etch is performed to removehorizontal portions of the physically exposed portions of the dielectricmaterial layer 60 within the second device region 200, while the secondpatterned mask layer 59 covers the dielectric stack (66, 68) and the atleast one first semiconductor material portion (3S, 3D, 3B) in the firstdevice region 100. A contiguous remaining vertical portion of thedielectric material layer 60 laterally surrounding, and contacting, thesecond gate structure (51, 53, 55) in the second device region 200constitutes a second gate spacer 64. Thus, the second gate spacer 64 canbe formed by anisotropically etching the second portion of thedielectric material layer 60 in the second device region 200 while thedielectric stack (66, 68) is masked in the first device region 100. Theanisotropic etch can be, for example, a reactive ion etch.

The second gate spacer 64 and the first gate spacer 62 include the samedielectric material, which is the material of the dielectric materiallayer. Further, the second gate spacer 64 has the same width as thefirst gate spacer 62. It is understood that the width of any gate spacerrefers to the lateral dimension of the bottommost portions of the gatespacer. Thus, the width of the first gate spacer 62 is measured at thebottommost portion thereof, and that the width of the second gate spacer64 is measured at the bottommost portion thereof.

Referring to FIGS. 10A and 10B, second active regions (4S, 4D) can beformed by introducing electrical dopants into portions of the at leastone second semiconductor material portions 40 that are not masked by thesecond gate structure (51, 53, 55) and the second gate spacer 64. Eachunimplanted portion of the at least one second semiconductor materialportion 40 constitutes a second body region 4B, which contacts a secondsource region 4S and a second drain region 4D at p-n junctions. Thesecond patterned mask layer 59 can be employed to prevent implantationof the electrical dopants into any portion of the at least one firstsemiconductor material portion (3S, 3D, 3B).

The second patterned mask layer 59 can be removed selective to thedielectric stack (66, 68), the at least one second semiconductormaterial portion (4S, 4D, 4B), the second gate spacer 64, and the secondgate structure (51, 53, 55), for example, by ashing. While the presentdisclosure is described employing an embodiment tin which the secondactive regions (4S, 4D) are formed after formation of the second gatespacer 64, embodiments in which the second active regions (4S, 4D) areformed prior to formation of the second gate spacer 64 are expresslycontemplated herein.

Second raised active regions (6S, 6D) can be formed by selectivedeposition of a semiconductor material on the surfaces of the secondactive regions (4S, 4D). During the selective deposition, thesemiconductor material is deposited only on semiconductor surfaces, anddoes not nucleate on dielectric surfaces such as the surfaces of thedielectric stack (66, 68), the second gate spacer 64, and the first andsecond dielectric caps (53, 55). Thus, the second raised active regions(6S, 6D) can be formed on the at least one second semiconductor materialportion (4S, 4D, 4B), while the dielectric stack (66, 68) in the firstdevice region 100 masks the at least one first semiconductor materialportion (3S, 3D, 3B). The second raised active regions (6S, 6D) areformed after the portion of the dielectric stack (66, 68) in the seconddevice region 200 is removed and while the portion of the dielectricstack (66, 68) in the first device region is present on the first raisedactive regions (5S, 5D).

The second raised active regions (4S, 4D) can be deposited with in-situdoping of electrical dopants, or can be deposited as an intrinsicsemiconductor material and subsequently doped with electrical dopants,for example, by a masked ion implantation process. The selectivedeposition can be performed, for example, employing a selective epitaxyprocess in which single crystalline semiconductor material portions areformed directly on the surfaces of the second active regions (4S, 4D).In this case, the second raised active regions (6S, 6D) can beepitaxially aligned to the at least one second semiconductor materialportion (4S, 4D, 4B).

Referring to FIGS. 11A and 11B, a diffusion barrier layer 72 can beoptionally formed on the top surfaces of the dielectric stack (66, 68),the insulator layer 20, the second raised active regions (6S, 6D), thesecond gate spacer 64, and the second gate stack (51, 53, 55). Thediffusion barrier layer 72 includes an oxygen-impervious material. Asused herein, an “oxygen-impervious material” refers to a material thatprovides molecular diffusivity for oxygen that is not greater than 10times the diffusivity of thermal silicon nitride in a temperature rangefrom 0° C. to 500° C. In one embodiment, the diffusion barrier layer 72can include silicon nitride. The diffusion barrier layer 72 can beformed, for example, by chemical vapor deposition or atomic layerdeposition. The diffusion barrier layer 72 can be conformal, i.e., canhave the same thickness throughout. The thickness of the diffusionbarrier layer 72 can be in a range from 3 nm to 60 nm, although lesserand greater thicknesses can also be employed.

A planarization dielectric layer 74 can be deposited over the over thefirst raised active regions (5S, 5D), the second raised active regions(6S, 6D), and the remaining portion of the dielectric stack (66, 68)that is present in the first device region 100. If a diffusion barrierlayer 72 is present, the planarization dielectric layer 74 can be formeddirectly on the diffusion barrier layer 72. The planarization dielectriclayer 74 can include undoped silicate glass, doped silicate glass,organosilicate glass (OSG), spin-on glass (SOG), or a combinationthereof. The planarization dielectric layer 74 can be formed by chemicalvapor deposition or spin-on coating. The planarization dielectric layer74 can include a self-planarizing material, or can be subsequentlyplanarized to provide a planar top surface.

Referring to FIGS. 12A and 12B, in case the gate structures (51, 53, 55)are disposable gate structures, the planarization dielectric layer 74,the diffusion barrier layer 72, and the topmost portion of thedielectric stack (66, 68) can be removed from above the horizontal planeincluding the top surfaces of the gate structures (51, 53, 55) by aplanarization process, a recess etch, or a combination thereof. The gatestructures (51, 53, 55) can be removed selective to the planarizationdielectric layer 74, the diffusion barrier layer 72, the dielectricstack (66, 68), the gate spacers (62, 64), and the semiconductormaterial portions (3S, 3D, 3B, 4S, 4D, 4B) to form gate cavities. Areplacement gate structure (80, 82) can be formed in each gate cavity.Each replacement gate structure (80, 82) can include a gate dielectric80 and a gate electrode 82. Various contact via structures 92 can beformed through the planarization dielectric layer 74, the diffusionbarrier layer 72, and the dielectric stack (66, 68).

The exemplary semiconductor structure includes a first gate structure(80, 82 in the first device region 100) straddling at least one firstsemiconductor material portion (3S, 3D, 3B) on a substrate (10, 20), asecond gate structure (80, 82 in the second device region 200)straddling at least one second semiconductor material portion (4S, 4D,4B) on the substrate (10, 20), first raised active regions (5S, 5D)located on the at least one first semiconductor material portion (3S,3D, 3B), second raised active regions (6S, 6D) located on the at leastone second semiconductor material portion (4S, 4D, 4B), a dielectricstack (66, 78) contacting the first raised active regions (5S, 5D) andthe first gate structure, and not in physical contact with the secondraised active regions (6S, 6D), and a material layer (72 or 74)including a dielectric material and in physical contact with thedielectric stack (66, 68) and surfaces of the second raised activeregions (6S, 6D). A first gate spacer 62 can laterally surround thefirst gate structure, and a second gate spacer 64 can laterally surroundthe second gate structure. The first gate spacer 62 and the second gatespacer 64 have the same composition and the same thickness as measuredat the bottommost portions thereof. All outer sidewalls of the firstgate spacer 52 can be in contact with one of the dielectric stack (66,68) and the first raised active regions (5S, 5D). The dielectric oxideliner 66 can contact the first raised active regions (5S, 5D). All outersidewalls of the second gate spacer 64 can be in contact with one of thematerial layer (72, 74) and the second raised active regions (6S, 6D).

While the disclosure has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Each of the embodiments described herein canbe implemented individually or in combination with any other embodimentunless expressly stated otherwise or clearly incompatible. Accordingly,the disclosure is intended to encompass all such alternatives,modifications and variations which fall within the scope and spirit ofthe disclosure and the following claims.

What is claimed is:
 1. A semiconductor structure comprising: a firstgate structure straddling a first semiconductor material portion on asubstrate; a second gate structure straddling a second semiconductormaterial portion on said substrate; a first gate spacer laterallysurrounding said first gate structure; a second gate spacer laterallysurrounding said second gate structure; first raised active regionslocated on said first semiconductor material portion; second raisedactive regions located on said second semiconductor material portion; adielectric stack contacting said first raised active regions and saidfirst gate structure, and not in physical contact with said secondraised active regions; and a material layer including a dielectricmaterial and in physical contact with said dielectric stack and surfacesof said second raised active regions, wherein all outer sidewalls ofsaid first gate spacer are in contact with one of said dielectric stackand said first raised active regions.
 2. The semiconductor structure ofclaim 1, wherein said first gate spacer and said second gate spacer havea same composition and a same thickness.
 3. The semiconductor structureof claim 1, wherein all areas of outer sidewalls of said second gatespacer are in contact with one of said material layer and said secondraised active regions.
 4. The semiconductor structure of claim 1,wherein said dielectric stack includes a dielectric oxide liner and adielectric nitride liner.
 5. The semiconductor structure of claim 4,wherein said dielectric oxide liner includes silicon oxide.
 6. Thesemiconductor structure of claim 4, wherein said dielectric oxide linercontacts said first raised active regions.
 7. The semiconductorstructure of claim 1, wherein said first raised active regions areepitaxially aligned to said first semiconductor material portion, andsaid second raised active regions are epitaxially aligned to said secondsemiconductor material portion.
 8. The semiconductor structure of claim1, wherein said dielectric material in said material layer is anoxygen-impervious material.
 9. The semiconductor structure of claim 1,wherein said substrate comprises an insulator layer and a handlesubstrate, and wherein said first semiconductor material portion andsaid second semiconductor material portion have a bottommost surface indirect physical contact with a topmost surface of said insulator layer.10. The semiconductor structure of claim 9, wherein said firstsemiconductor material portion and said second semiconductor materialportion are semiconductor fins.
 11. The semiconductor structure of claim1, wherein said first gate structure and said second gate structurecomprise a gate dielectric and a gate electrode, wherein a topmostsurface of said gate dielectric is coplanar with a topmost surface ofsaid gate electrode.
 12. The semiconductor structure of claim 11,further comprising a planarization dielectric layer located surroundingsaid first gate structure and said second gate structure, wherein atopmost surface of said planarization dielectric layer is coplanar withsaid topmost surfaces of said gate dielectric and said gate electrode.13. The semiconductor of claim 1, wherein said first gate structure andsaid second gate structure comprises a gate stack of, from bottom totop, a gate dielectric and a gate electrode, wherein said gatedielectric is located entirely beneath said gate electrode.
 14. Asemiconductor structure comprising: a first gate structure straddling afirst semiconductor material portion on a substrate; a second gatestructure straddling a second semiconductor material portion on saidsubstrate, wherein said first gate structure and said second gatestructure comprise a gate dielectric and a gate electrode, wherein atopmost surface of said gate dielectric is coplanar with a topmostsurface of said gate electrode; first raised active regions located onsaid first semiconductor material portion; second raised active regionslocated on said second semiconductor material portion; a dielectricstack contacting said first raised active regions and said first gatestructure, and not in physical contact with said second raised activeregions; a material layer including a dielectric material and inphysical contact with said dielectric stack and surfaces of said secondraised active regions; and a planarization dielectric layer locatedsurrounding said first gate structure and said second gate structure,wherein a topmost surface of said planarization dielectric layer iscoplanar with said topmost surfaces of said gate dielectric and saidgate electrode.
 15. The semiconductor structure of claim 14, furthercomprising: a first gate spacer laterally surrounding said first gatestructure; and a second gate spacer laterally surrounding said secondgate structure.
 16. The semiconductor structure of claim 15, wherein allouter sidewalls of said first gate spacer are in contact with one ofsaid dielectric stack and said first raised active regions.